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    Mechanisms of Silica Scale Formation on Organic Macromolecule-Coated Surfaces

    Year: 2021

    Journal: ACS ES&T Wat., Volume 1, AUG 13, page 1826–1836

    Authors: Qi, Yarong; Tong, Tiezheng; Liu, Xitong

    Organizations: Cross-Disciplinary Research Fund at The George Washington University

    Keywords: silica scaling; organic macromolecules; foulants; hydrophilicity; nucleation; quartz crystal microbalance; force spectroscopy

    While the presence of organic macromolecules (or foulants) can exacerbate silica scaling of membranes, the effects of the types and physicochemical properties of macromolecules on silica scale formation remain poorly understood. We herein use a quartz crystal microbalance with dissipation monitoring to investigate the kinetics of silica mass deposition on sensors coated by lysozyme, bovine serum albumin (BSA), humic acid, or alginate. Our results show that deposited silica mass resulting from heterogeneous nucleation of monosilicic acid cannot be explained by the free energy barrier to nucleation but instead linearly correlated to the hydration energy of the macromolecule-covered surfaces. The most silica heterogeneous nucleation occurs on the most hydrophilic alginate-coated surface, which is likely due to the favorable interaction between silicic acid and alginate via hydrogen bonding and chemical reactions. For the deposition of silica aggregates formed from bulk nucleation, the deposited silica mass is the highest on the BSA-coated surface, consistent with the greatest adhesion force between BSA and silica measured using force spectroscopy. Finally, silica scaling on macromolecule-coated surfaces is promoted by calcium ions, and the deposition of silica is mostly irreversible upon rinsing with water.
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